Pergamon Po/yhedron Vol. 13, No. 4, pp. 701-708, 1994 Coovrkht 0 1994 Elsevier science Ltd Printedih &a~Britain. All rights nxerwd 0277~5387194 S6.OO+O.O0 DINUCLEAR COMPLEXES OF RHENIUM(V) WITH AMINE- PHENOL LIGANDS : SYNTHESES, CHARACTERIZATION AND X-RAY CRYSTAL STRUCTURES M. R. A. PILLAI,* C. L. BARNES and E. 0. SCHLEMPERt Department of Chemistry, University of Missouri-Columbia, Columbia, MO 65211, U.S.A. (Received 11 March 1993 ; accepted 12 August 1993) Abstract-Rhenium(V) complexes of three amine-phenol ligands prepared by reducing Schiff bases derived from salicylaldehyde and 1,3_diaminopropane and 1 ,Cdiaminobutane, as well as 1,3_diaminopropane and 2-hydroxyacetophenone, have been synthesized. ‘H and 13C NMR and IR spectroscopy were used for characterization of two of the complexes. X- ray diffraction data of all the three complexes were collected by the 8-20 scan method using MO-& radiation. The structures were solved by Patterson and Fourier methods and refined to final R factors of 0.046, 0.032 and 0.052, respectively for the three complexes. The complexes are dinuclear with O=Re-O-Re=O backbones and near octahedral Rev coordination. Two of the structures of the complexes are isomorphous with the structures obtained earlier for corresponding technetium complexes. zyxwvutsrqponmlkjihgfedcbaZYXWVUTS lg6Re and la8Re, B particle emitting isotopes of the element rhenium, are finding application for the development of radiopharmaceuticals for radio- therapy. ‘-I Hence there is an increasing interest in the coordination chemistry of rhenium to develop new ligand systems and bifunctional chelating agents which might find use in radiopharmaceutical applications. We have reported the syntheses and characterization of tetradentate amine-phenol ligands and their complexes with ggmT~.S Studies at macroscopic levels with “Tc showed that these ligands form dinuclear complexes, technetium being hexacoordinated to two amine nitrogens, two oxy- gens from the phenols and two axial oxygens, of which one forms the ,u-0x0 bridge between the two technetium atoms in the dinuclear complexes. Rhenium, being a congener to technetium in group VIIa, might be expected to form complexes that have structural and biological similarities to cor- responding technetium complexes.6 Hence we were interested in exploring the coordination chemistry of the rhenium complexes with amine-phenol *Present address : Isotope Division, Bhabha Atomic Research Centre, Bombay 400 085, India. TAuthor to whom correspondence should be addressed. ligands. We have prepared and characterized the rhenium complexes of two amine-phenol ligands which were studied earlier by us with “Tc. A third amine-phenol ligand was synthesized which has two asymmetric carbon atoms. This class of chiral ligands was synthesized to study and com- pare the in vivo uptake of the complexes of optically active isomers with that of the corresponding ligands without optical activity.7 The rhenium com- plex of one such amine-phenol complex with chiral carbons was also studied in this work. Figure 1 shows the ligands used in these studies. EXPERIMENTAL NH4Re04 was obtained from Aldrich. All com- mon chemicals and solvents used were of reagent grade. K2ReOC1, intermediate was prepared by reduction of NH,ReO, with KI and HC1.8 The syn- thesis and characterization of ligands 1 and 2 have been described in detail.5 Measurements ‘H and proton decoupled 13C NMR spectra were recorded on a Bruker AMX 500 spectrometer, 500 701